1. Field of the Invention
The present invention relates to a band saw blade sensor and control system which will sense deviation of a continuous flexible metal saw blade during a cutting operation and will implement adjustments thereto.
2. Prior Art
One type of band saw employs a flexible, continuous metal band saw blade which circulates at high speed around a pair of pulleys, at least one of which is driven by a motor.
Various types of material bar may be cut, such as large metal bars or ingots. Material to be cut may be brought to the band saw by a material handling feed table, such as shown in Applicant's prior patent—Harris (U.S. Pat. No. 8,893,873).
An existing problem with continuous metal saw blades is that the flexible blade is known to move or migrate during a cutting operation for a number of reasons. The blade itself has a front side and a back side which is adjacent to the large bar of material and the material handling feed table. Since the backside of the blade will dull with use, the blade tends to deviate toward the opposed, sharper edge.
In addition, the blade is held in tension and therefore, when the blade is pushed too fast or with too much pressure into the material, the blade will start to deviate, resulting in deflection of the saw blade.
A variety of proposals have been made in the past to alter positioning of the continuous band saw blade.
For example, Dietz et al. (U.S. Pat. No. 8,250,954) discloses a method of positioning a band saw blade. Guides 40 and 42 are positioned on opposed sides of a saw table. Guide 40 includes a machine-mounted guide block 44 and a magnet guide 46. Electromagnets exert magnetic force on the saw blade. Accordingly, the saw blade may be oriented obliquely or may compensate for a lateral evasive movement. The electromagnetic force is used to alter the position of the blade. The system would not work when cutting ferrous metal pieces, which would interfere with the magnetic forces.
Viljanen (U.S. Patent Publication No. 2008/0302227) discloses a band saw blade adjustment system with electronically controlled electric magnet element 6 providing repulsion or a pulling force on the saw blade. A mechanical or electronic distance detector senses change in the blade position. The system would only work when cutting non-ferrous materials.
Hauser (U.S. Pat. No. 4,437,367) discloses controlling the tensile strength of a saw band to prevent strain. A beam on two supports A permits sagging or bending of the saw band in a vertical plane as shown in FIGS. 8 and 9, which is sensed by a magneto-resistor field plate potentiometer 31. The feed rate velocity is thus controlled although no control of the band tension is taught or suggested.
Wijesinghe et al. (U.S. Pat. No. 5,237,897) discloses an automatic strain and saw tracking method including a strain control mechanism to maintain a desired strain and a lifting mechanism to vary the track of the saw.
Notwithstanding the foregoing, it would be desirable to provide an improved band saw blade sensor and control system utilizing inductive sensors to sense deviation of the blade during a cutting operation by utilizing magnetic fields.
It would further be desirable to provide a band saw blade sensor and control system which could take at least two actions in response to deviation of the band saw blade—the band tension could be adjusted and, second, the set point of the blade force on the work piece could be adjusted in order to bring the blade back into alignment.
It would further be desirable to provide a band saw blade sensor and control system which would select between adjustment of the band tension and adjustment of the blade force dependent on a variety of pre-selected factors.